1. Field of the Invention
The present invention relates to an ink-jet water-based ink, an ink-jet recording method, an ink partridge and an ink-jet recording apparatus, and particularly to a coloring-material-dispersed water-based ink high in ejection stability and good in coloring of images formed from this ink and suitable for use in ink-jet recording, and an ink-jet recording method, an ink cartridge and an ink-jet recording apparatus using this ink.
2. Related Background Art
Water-based inks using a water-soluble coloring material have heretofore been often used as ink-jet inks. In recent years, attention has been paid to water-insoluble coloring materials excellent in fastness properties such as water fastness and weatherability, such as pigments, and various attempts have been made. Since the water-insoluble coloring materials are not dissolved in water, a method using an ink containing such a coloring material as a non-aqueous ink is employed. Japanese Patent Application Laid-Open No. 2000-17211 has proposed a non-aqueous ink to which polyoxyethylene castor oil is added. However, there are many limitations to use the non-aqueous ink as an ink-jet ink, and care is required even from the viewpoint of safety. There is thus a demand for development of a water-based ink using a water-insoluble coloring material. In order to use the water-insoluble coloring material as a coloring material for water-based inks, it is required to stably disperse the water-insoluble coloring material in an aqueous medium, and a coloring-material-dispersed water-based ink obtained by adding a dispersant such as a polymeric compound or surfactant to uniformly disperse the water-insoluble coloring material in the aqueous medium is required.
When such a coloring-material-dispersed water-based ink is used in ink-jet recording, it is attempted to cause the water-insoluble coloring material in the ink to have an aggregating function and a water-insolubilizing function for the purpose of improving the fixability and water fastness of the ink on paper. However, the dispersion stability of the water-insoluble coloring material in the ink comes to be lowered by allowing the water-insoluble coloring material to have such functions, which involves such problems that the water-insoluble coloring material tends to aggregate during storage of the ink to cause density unevenness and precipitation, and clogging at orifices of an ink-jet recording apparatus by drying of the ink is easily caused to lower the ejection stability of the ink. Since the water-insoluble coloring material is easy to aggregate on the surface of a recording material, a printed image also has a problem that saturation is greatly lowered due to light scattering caused by aggregated particles to deteriorate the color developing property of the ink.
In order to solve the above-described problems, there has been proposed an ink containing a polyoxyalkylene (see Japanese Patent Application Laid-Open No. H10-53741). However, the proposed ink yet has no effect to improve ejection stability of the ink, and in the case where the composition of the ink is greatly changed, such as the case where the ink is concentrated at orifices, which is always caused when the ink is used in an ink-jet recording apparatus, the dispersion stability of the water-insoluble coloring material in the ink is liable to be lowered. Therefore, the water-insoluble coloring material greatly adheres to peripheral portions of nozzles of the ink-jet recording apparatus, so that ejection failure and dot misalignment are easy to occur. Thus, this ink does not yet reach a level satisfying the ejection stability. In particular, in the case of an ink-jet recording apparatus having a line head, the cleaning and recovering operation of ink-jet nozzles of which cannot be frequently conducted, the occurrence of the ink ejection failure and dot misalignment becomes a big problem.